Injection of vanadium ions by the laser blowoff technique has permitted the impurity content in TFR plasmas to be modified purposely before ion cyclotron resonance (ICR) heating experiments in the mode conversion regime. The initial rate of increase in the central deuteron temperature TD(0) has thus been enhanced. By solving the wave propagation equation in the WKB approximation, it has been possible to account for the enhanced dTD(0)/dt value by wave energy deposition on resonating V21+ ions, provided a fraction (of the order of 10%) of these ions has been accelerated to the tens of keV range. Previous experimental ICR heating results, in conditions such that the proton cyclotron layer is outside the limiter radius, can be explained by similar resonance processes on intrinsic metal impurity ions.
Application of the intermediate frequency range fast wave to the JIPP TII-U plasma